The invention is preferably used in data transmission systems employing orthogonal frequency division multiplexing (OFDM), in particular in wireless applications for digital video broadcasting (DVB, e.g. DVB-H, DVB-T), but can also be used for other transmission modes, such as ISDB-T, DAB, WiBro and WiMax. DVB, e.g. DVB-H and DVB-T are known standards for bringing digital television content for instance to mobile devices.
Such orthogonal frequency division multiplexing systems are very sensitive to the intersymbol interference (ISI), which is caused by the loss of orthogonality of the symbols. The invention relates to the compensation of the intersymbol interference by estimating a symbol time error.
The orthogonal frequency division multiplexing mode is a mode which converts a stream of symbols in a frame into parallel data of a block unit and then multiplexes the parallel symbols into different sub-carrier frequencies. The multi-carrier multiplex has the property that all carriers are orthogonal to one another with respect to a certain length that is typically 2n such that a fast Fourier-transformation can be used. The OFDM mode is implemented with the discrete Fourier-transformation (DFT) at a receiver and the inverse discrete Fourier-transformation (IDFT) at a transmitter, which is simply obtained by the orthogonal property and the definition of the discrete Fourier-transformation.
In broadband transmission systems, a guard interval is formed by a cyclic extension preceding the output of the inverse discrete Fourier-transformation for each OFDM symbol.